Black cabs "capable of zero tail pipe emission operation" will start to appear on the streets of London by the year 2020 under plans announced yesterday by mayor Boris Johnson.
Hurry, Boris, hurry!
The commitment comes as part of the mayor's new Air Quality Strategy (pdf), aimed at cleaning up various kinds of atmospheric …

VW Polo

Swappable battery packs?

I'm impressed to see that the Reg has a clear idea of what technology will be available in 2020 for electric cars. Wonder if it's possible to invent swap-in/out battery packs by then which could be used in a fleet of taxis, to avoid individual taxis having to sit around charging all day?

Re: Swappable battery packs?

Black cabs are one of the few areas where I can see swappable battery packs being a sensible solution.

For this tech to work you would need a reasonable number of vehicles that regularly need a full recharge, fast, (rather than being OK with a top-up overnight) and where speed is worth paying for. You would also need a massive infrastructure (ideally within a limited area) with staff testing battery packs and even the ability to drive a new pack out to a stranded vehicle if a pack fails for some reason. It would also help considerably if every vehicle in the scheme was of the same design. There would also need to be financial and regulatory reasons to switch to this tech. And finally you really want all involved to be members of some sort of organization that can arbitrate disputes and educate users (maybe even manage financing).

All in all, I think battery-swap cabs would be a great idea. Especially if charging stations charge off-peak and can give back some power when there are sudden demand peaks.

Taxi Ranks

Have the battery mounted under the taxi rather than in it, it pulls up at a taxi rank with an evalated pedestrian loading area.

Tray slides out from under the pedestrian area to take the old battery out, and put the new one in and stores the battery under the pedestrian area.

You only need a method of positioning the battery accurately before pushing it back up under the taxi, and that could be done with mechanical guides rather than expensive optical robotics. A 5 minute job.

Railway stations would be especially good spots for this because they already have the high power electric connections which would be needed for onsite charging.

No special trips needed for the Taxi, it's just going back to a central location it would probably be going to at some point during the day anyway.

do the math

Re: Re: Swappable battery packs?

Deploy charging stations at places where you already have a large number of cabs naturally waiting on a regular basis like railway station and airport taxi ranks. Smaller charging stations could also be deployed at major hotels. Of course, you already have part of the infrastructure in the form of existing petrol stations.

yup

Redox flow batteries?

The alternative to switching out the whole battery is a redox flow battery where you just swap out the spent electrolyte and replace it with fresh electrolyte. The spent electrolyte is then recharged for reuse. Down time is no more than filling a car with petrol.

Way faster and mechanically simpler than swapping out whole batteries.

Re: Hydrogen

"but hydrogen supplies would be an issue"

Forgive me if I'm wrong, but doesn't London have a huge river going through it, with 2 tidal surges per day. If the Thames Gateway can generate 128GWh of leccy per hour, why can't they build another, much smaller if necessary that simply sits there cracking water on demand all day long, straight into the tanks of an orderly queue of Taxis? Once the the initial build cost is out of the way, the project is pretty much self sufficient. The water comes from the river, the power to crack it comes from the river, and when the hydrogen is combusted, it turns into more water, that goes via the water cycle, and probably ends up back in the river. Not exactly perpetual motion, but build cost out of the way, the only thing this will need is maintenance to make sure the cogs dont seize up and tanks don't leak.

Hydrogen won't work

Hydrogen is difficult to work with due to the small size of the molecule -- hard to compress and passes right through materials that can contain other gasses. This leaking hydrogen would not recombine with the oxygen it was originally bound to, resulting in less water on the planet. Plus the whole water --> hydrogen+oxygen --> water fuel cell idea is at best about 60% efficient.

The entire thing is dendent on taxation

OK, so what will be the guarantee that by 2020 we will not see electricity colouring (hello red diesel) and cars being chipped to ensure they accept only leccy from a "duty-paid" outlet.

This is trivial - just run a data over power protocol similar to X10 both ways and transmit a challenge/response before opening the "pipe".

The entire dubious economical benefit of electric vehicles is dependent solely upon taxation. I do not quite see them surviving through being taxed and let me put it this way - with the amount of revenue the crown gets from fuel duty "chipped leccy" future _WILL_ come. It is not a question of "if", it is a question of "when". If leccy vehicles become sufficiently mass market to be taxis by 2020 they will definitely be taxed. HMG initiative to have "smart meters" in every house by that time will happily provide the necessary tax accounting, collection and enforcement.

Bumper car?

Suddenly, that joke of the new strategy for leccy cars built by Alpha Romeo doesn't seem far fetched. It would work just as trains. Fully leccy, and unlimited range, if you keep it inside the grid. No worries about batteries either. Actually, it looks like a pretty good idea!

Old Idea

Not a good solution

The problem is that London is over-crowded. The streets have got too much traffic and the public transport system is hopelessly inadequate. So, of course they decide to build more offices and higher offices to make things worse!

Terrible idea

The only way to achieve this is with hydrogen, safer than petrol and can be produced for less.

Plus it gives more range than electric cars and the fuel cells don't cost as much as batteries to replace and won't degrade even half as fast as a battery will on an electric car.

Hydrogen is already used in Japan for buses with no complaints.

Electric cars becoming widespread will lead to blackouts, higher electricity costs, and an 8 hour wait to refill your car (and you don't want to do it in the day)

In the short run, swapping oil for electric means we need more nuclear plants or coal fired ones, more hotels across the country as a long trip is out of the question in an electric car, less petrol stations will be able to stay in business as cars will be there overnight to charge and finally batteries have to be replaced after about 3 years and currently cost £30,000 each.

@Tigra

RE: Dave Fail

Hydrogen can be produced through electrolysis in your own garage or from solar panels on the roof of petrol stations, both costing less than peak oil.

Hydrogen burns upwards quickly while petrol explodes and burns for much longer, while spreading out.

You don't know what you're talking about Dave, and using the "May contain highly technical information" picture and then offering a rebuttal with no supporting argument is just lazy and a massive fail.

Erm

Not to butt in on a perfectly good argument but....

Electrolysis requires electricity, and isn't 100% efficient. So you're actually just running an electric car but with an intermediate step of storage of a highly flammable material under high pressure (you have to pressurise the hydrogen to store any decent amount of it). And if you're doing conventional water electrolysis, you're doing so in the vicinity of huge amounts of highly-oxidising... well... oxygen. Read "explosion waiting to happen". This is why the Hindenburg was a bad idea, by the way - it stored huge amounts of hydrogen.

And solar panels? Really? You know the ecological impact of them and the amount of power they can *actually* produce and the amount of infrastructure they require to store it for the other 16 hours of the day? You'd be lucky to generate enough for a car journey or two in a car (if you're talking intermediate electrolysis) from a petrol-station sized solar panel, and you'd have more lead, acid, copper and plastic than you would solar panel. All of that has to have had used energy to extract it, refine it, combine it, package it, ship it and replace it. You really are no better off.

And notice how *everything* comes back to electricity, plastics, semiconductors, rare-earth materials, extremely high precision engineering, transporting heavy stuff to lots of places around the country and constantly repairing it etc. all the time? Don't think fancy methods - think volume. You need the energy to push a car several hundred miles on a tank. That energy, eventually, comes from electricity (e.g. solar). How much impact and time does it take to generate that amount of energy from your method of generation even with 100% efficiency? (e.g. solar = all day, coal-fired power grid = fraction of a second). Now factor in just how many other items are required, just how many transfers (e.g. thermal -> electrical -> chemical -> electrical -> physical) etc. are required, their efficiencies etc.

Electric cars are *STILL* a nonsense. When we can get a solar panel that can literally power an entire car to run 16 hours a day from a square meter on the top of its roof, then it's worthwhile. Until then, you're just putting "green-looking" steps into an inherently "ungreen" process and ignoring everything else you've done wrong.

Electric cars are good for milk floats. They were 30 years ago and they didn't *pretend* to be green - they AREN'T - but the tech that drives your modern electric car is actually inherently WORSE in green credentials than a 30-year-old milk float.

"When we can get a solar panel that can literally power an entire car"

(Untitled)

Yeah, I know. I wasn't going to mention that. Solar is really a crock.

But it's the transfers and origins that matter, not what fancy new technology you use. If the energy to run your car comes from solar power originally, then it's quite simple to work out Watts required and how large/efficient a solar panel you'd need to do a single journey. If you assume less than 50% efficiency overall for such things as transfers, conversions, storage losses, etc. then you'll see if it's even *viable* (and that just assumes you *can* get losses down to 50% at all). If doesn't matter if it's via hydrogen, direct electric, compressed air or whether you're synthesising oil, it's the origin of the energy that matters.

Electric cars work. But somewhere you're burning 80kW worth of coal, or a huge FIELD of wind/wave/solar power at very inefficient ratios rather than 80kW worth of petroleum. I know very well that we don't have much of that left, but until even *one* of the renewables technologies can compete on a real scale (without subsidies, taking its lifespan into account, actual envrionmental cost of setup and maintenance etc.) it's a waste of time and we're just burning coal / oil / gas / uranium in order to make up for the low, unreliable yield of a field full of plastic towers stuck in a hostile environment that are difficult to repair.

Personally, I just think that petrol cars will get more efficient (efficiency hasn't really been a selling point historically) and then we'll find a slightly different grade of petrol that people can run on in the meantime and that's easier to find (e.g. we'll go back to 90 octane instead of 95/98 or something). People are more likely to own an LPG car in the next ten years than they are an electric car.

Wow

Size Matters, too!

I reckon it'll be a good idea to try getting black cabs electrified. Swappable battery packs (see previous) have a number of advantages (and disadvantages) but the feasibility gathers more pace if the actual size of the cabs is reduced. On the odd occasion I go to London I see hundreds of cabs with only 1 or 2 people in them. Hulking great lumps of metal they are too*!! Make them smaller and lighter and the efficiency improves greatly. Make it obvious to the customer whether they're good for 3, 4 or 5 passengers and we may be on to something.

Recharging

From what little I know of the taxi trade, the article seems rather pessimistic.

Don't taxi drivers spend a significant part of the day parked, either in taxi ranks or taking (legally mandated?) breaks? If these were equipped with fast charging technology, then a taxi could be recharged several times per day, not just once.

Equipping taxi-only locations with fast charging facilities would be easier than rolling them out to the general motoring population. Similarly battery-swap stations would be easier for a fleet of standardised London taxis.

Or...

Regenerative braking

Another thing not mentioned is that cars with batteries employ regenerative braking. The greater the amount of start-stop driving, the greater the advantage of this technology, even if it's a hybrid with little electricity storage capacity. London taxis probably do more start-stop than any other sort of motorist. Why don't they take the drive system from a Prius and put it in a taxi? (as a solution that's available now)

Also in passing - why isn't there a van variant of a Prius? City centre vans are probably nearly as much start-stop as taxis but I'd guess lower annual mileage because more time stopped loading and unloading.

They're working on it...

Why no mention of CNG

Why no mention of compressed natural gas? True, it's still a fossil fuel. However, less CO2 emissions than diesel, and extremely clean-burning.

The barrier with respect to ordinary motorists is whether they be trusted with a high-pressure gas cylinder, and especially with the refilling thereof? That's less of an issue for professional drivers with strong vehicle inspection regimes already in force.

The title is required, and must contain letters and/or digits

compressed not liquified

It takes more energy to liquify a gas that in does to compress it. Your land cruiser can use it too. Lots of buses where I live are using CNG now, and a few using re-newable CNG captured from the rubbish tip. Although cost from that is a bit more expensive because of the extra filtration or something.

CNG <> LPG

LPG is liquid propane gas (could also be low pressure gas). It's not under high pressure, it's not a great hazard, the public can buy cans of it for blowtorches, camping cookers, etc. and in rural areas houses have large tanks of the stuff as their domestic gas supply delivered by even larger tanker lorries.

CNG is compressed natural gas, ie methane. To store a useful amount in a vehicle means a very high gas pressure.

@Nigel 11

"Why no mention of compressed natural gas? True, it's still a fossil fuel. However, less CO2 emissions than diesel, and extremely clean-burning."

Actually it doesn't *have* to be.

ElReg reported a British Gas funded study that (yes not very likely to be a low priced supplier) that estimated that 50% of the current UK gas supply could be met by anaerobic digestion of putrifiable waste (that's meat, soft fruit, animal slurry. Basically anything not loaded with lots of cellulose and chlorophyll)

cheap electricity: nice while it lasts

Do you have a downer on hydrogen fuel cells?

Isn't it curious that neither the fourth estate nor the politicians that feed them with press releases can be bothered to remember/research stuff on any particular scientific or engineering topic?

For instance, last week Boris's Deputy Mayor Kit Malthouse launched the first two of eight hydrogen fuel cell buses (which will be used on route RV1). These are not trial buses, they are *production* units. The (much smaller) trial buses have been running on the route for several years.

Once more fueling infrastructure is in place there seems to be a genuine desire to have more such buses on other routes. And this is 1st Bus's take, not some pie eyed greenery eating surrender monkey.

It follows that, with a bit creative thinking on the part of TfL, that infrastructure could be used by other transport providers such as licensed taxis. Hopefully before the first lithium battery fire occurs in an electric car.

If you want to send it as a liquid you're looking at "Vacuum jacketed" IE *concentric* welded stainless steel lines with a vacuum between. Liquefying it take 1/3 of the energy carried per unit mass of H2 your liquefying.

So factor in an *extensive* pipe laying operation across London if you want to do this the *proper* way.

That suggests they will make H2 by catalytic processing of natural gas, a *highly* energy intensive process to produce the "clean" fuel. They will then take a shed load *more* energy either to compress it to a reasonable volume or liquefy it.

My point is that Hydrogen has a *lot* of problems which make the idea of it as a "drop in" replacement for *any* fuel ridiculous.

Key point. Hydrogen is an *exceptionally* awkward energy carrier (not a primary fuel. It's only found raw in interplanetary space at a few atoms per m^3) to make, transport and store due to its natural *physical* properties, which don't change unless you live somewhere like Pluto.

It has *very* poor energy *density*. 1 kg of gasoline gives c62Mj at roughly 1.4l. 1Kg of H2 gives c112Mj at c12.9l (*If* it's at -253c), but as you've spent 1/3 of that to liquefy it in the first place. 20% more energy at only 820% more volume.

H2 is stored at either -253c (that's *very* cold) or 5000psi or 34.5Mpa (about 345 atmospheres). The USAF issues TNT equivalents on containers pressurised to this level. A bus using this storage method should be good several kilos of TNT.

No doubt the buses have passed crash testing but at the end of the day we'll know what *really* happens if there is a serious crash. *Hopefully* the tanks will vent and a fountain of H2 will spurt up into the sky and disperse before it ignites (IIRC H2 explodes in air at >4% and <96% H2 concentrations). If not and you're nearby you will see an interesting example of a gas/air explosion. Sometimes referred to as a poor mans atomic bomb.

James May was very impressed by the LH2 Honda he drove in the US some time ago on Top Gear. The issues he identified are *very* relevant to getting acceptance of non fossil fuel powered vehicles.

However his grasp of engineering practicality is about about as sound as my grasp of playing a Bach Concerto.